In conventional die casting machines, a ladle method has been commonly employed for supplying an aluminum melt to a plunger sleeve. According to the ladle method, an aluminum melt is drawn from a melting furnace by means of a ladle and supplied to a plunger sleeve.
As a technique to take the place of the ladle method, a melt supply pipe method has recently been attracting attention. The melt supply pipe method involves directly connecting a melting furnace and a plunger sleeve with a melt supply pipe, and supplying an aluminum melt through the melt supply pipe to the plunger sleeve. Mixing of an aluminum oxide film or solid broken pieces into an aluminum melt can be significantly reduced by the melt supply pipe method as compared to the conventional ladle method. The melt supply pipe method thus has the advantage that it can provide a higher-quality die-cast product.
A conventional melt supply pipe, which has so far been used to connect a melting furnace and a plunger sleeve, has a structure in which a heater is wrapped around a ceramic pipe. A ceramic material, because of its high melting loss resistance to an aluminum melt, is used for a melt supply pipe.
While a ceramic pipe is strong to an aluminum melt, it is weak to impact and can be broken by its vibration during operation or by erroneous handling upon its maintenance. Further, only an insufficient clamping load can be applied on a connecting portion of such a breakable ceramic pipe, which could cause leakage of an aluminum melt from the connecting portion.
The applicant has proposed an aluminum melt-contact member having enhanced melting loss resistance to an aluminum melt, comprising a steel base, a Ni alloy layer formed on the steel base, and TiC bonded in a particulate state to the surface of the Ni alloy layer (Japanese Patent Laid-Open Publication No. 2005-264306).